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<div class="highlight"><pre><span></span><span class="ch">#!/usr/bin/python</span>
<span class="c1"># The contents of this file are in the public domain. See LICENSE_FOR_EXAMPLE_PROGRAMS.txt</span>
<span class="c1"># </span>
<span class="c1"># This simple example shows how to call dlib&#39;s optimal linear assignment</span>
<span class="c1"># problem solver.  It is an implementation of the famous Hungarian algorithm</span>
<span class="c1"># and is quite fast, operating in O(N^3) time.</span>
<span class="c1">#</span>
<span class="c1"># COMPILING/INSTALLING THE DLIB PYTHON INTERFACE</span>
<span class="c1">#   You can install dlib using the command:</span>
<span class="c1">#       pip install dlib</span>
<span class="c1">#</span>
<span class="c1">#   Alternatively, if you want to compile dlib yourself then go into the dlib</span>
<span class="c1">#   root folder and run:</span>
<span class="c1">#       python setup.py install</span>
<span class="c1">#</span>
<span class="c1">#   Compiling dlib should work on any operating system so long as you have</span>
<span class="c1">#   CMake installed.  On Ubuntu, this can be done easily by running the</span>
<span class="c1">#   command:</span>
<span class="c1">#       sudo apt-get install cmake</span>
<span class="c1">#</span>

<span class="kn">import</span> <span class="nn">dlib</span>

<span class="c1"># Let&#39;s imagine you need to assign N people to N jobs.  Additionally, each</span>
<span class="c1"># person will make your company a certain amount of money at each job, but each</span>
<span class="c1"># person has different skills so they are better at some jobs and worse at</span>
<span class="c1"># others.  You would like to find the best way to assign people to these jobs.</span>
<span class="c1"># In particular, you would like to maximize the amount of money the group makes</span>
<span class="c1"># as a whole.  This is an example of an assignment problem and is what is solved</span>
<span class="c1"># by the dlib.max_cost_assignment() routine.</span>

<span class="c1"># So in this example, let&#39;s imagine we have 3 people and 3 jobs. We represent</span>
<span class="c1"># the amount of money each person will produce at each job with a cost matrix.</span>
<span class="c1"># Each row corresponds to a person and each column corresponds to a job. So for</span>
<span class="c1"># example, below we are saying that person 0 will make $1 at job 0, $2 at job 1,</span>
<span class="c1"># and $6 at job 2.</span>
<span class="n">cost</span> <span class="o">=</span> <span class="n">dlib</span><span class="o">.</span><span class="n">matrix</span><span class="p">([[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">6</span><span class="p">],</span>
                    <span class="p">[</span><span class="mi">5</span><span class="p">,</span> <span class="mi">3</span><span class="p">,</span> <span class="mi">6</span><span class="p">],</span>
                    <span class="p">[</span><span class="mi">4</span><span class="p">,</span> <span class="mi">5</span><span class="p">,</span> <span class="mi">0</span><span class="p">]])</span>

<span class="c1"># To find out the best assignment of people to jobs we just need to call this</span>
<span class="c1"># function.</span>
<span class="n">assignment</span> <span class="o">=</span> <span class="n">dlib</span><span class="o">.</span><span class="n">max_cost_assignment</span><span class="p">(</span><span class="n">cost</span><span class="p">)</span>

<span class="c1"># This prints optimal assignments:  [2, 0, 1]</span>
<span class="c1"># which indicates that we should assign the person from the first row of the</span>
<span class="c1"># cost matrix to job 2, the middle row person to job 0, and the bottom row</span>
<span class="c1"># person to job 1.</span>
<span class="k">print</span><span class="p">(</span><span class="s2">&quot;Optimal assignments: {}&quot;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">assignment</span><span class="p">))</span>

<span class="c1"># This prints optimal cost:  16.0</span>
<span class="c1"># which is correct since our optimal assignment is 6+5+5.</span>
<span class="k">print</span><span class="p">(</span><span class="s2">&quot;Optimal cost: {}&quot;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">dlib</span><span class="o">.</span><span class="n">assignment_cost</span><span class="p">(</span><span class="n">cost</span><span class="p">,</span> <span class="n">assignment</span><span class="p">)))</span>
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